Conventionally, tuned mass damper (TMD), a device consisting of a mass, a spring and a damper, is simple in structure and requires no power input. When the natural frequency of TMD matches the frequency of a main structure, vibration of the main structure makes the TMD to vibrate in resonance, dissipating a substantial amount of vibration energy of the main structure. Therefore, TMD is widely employed in vibration control for bridge, high-rise building, machine tools and many other engineering systems.
It can be seen that the conventional TMD could exert damping effect only when its natural vibration frequency matches the vibration frequency of the main structure. That is, as the vibration frequency of the main structure varies, it would decrease the effect of TMD or cause TMD to fail.